Micellar Solutions Research Articles

Micellar solubility and co-solubilization of fragrance raw materials in sodium dodecyl sulfate and polysorbate 20 surfactant systems.

The aim of this work was to investigate the solubility and co-solubilization of fragrance raw materials (FRMs) in sodium dodecyl sulfate (SDS) and polysorbate 20 (P20) surfactant micellar systems, which can advance our knowledge of multi-solute micellar solubilization and fragrance olfactory performance from product matrices containing the surfactants. The transfer of individual FRMs and binary FRM mixtures into micellar phases was quantified by UV-VIS differential spectroscopy and evaluated in terms of the standard Gibbs free energy change and micelle-water partition coefficient. Co-solubilization effects were further evaluated by the deviation ratio. Anionic SDS was found overall to be a more efficient solubilizer than nonionic P20. On an individual basis, micellar solubilization generally increased with solute lipophilicity but was additionally impacted by solute rigidity and steric effects. Micellar solubilization was favoured for more rigid structures and less favoured for FRMs that exhibited larger molecular rotation and steric hindrance. For multi-solute systems, three co-solubilization effects were observed: (i) inhibitive effect in which micellar partitioning of both solutes decreased, (ii) an inverse effect where partitioning of one solute increased while the other decreased and (iii) synergistic effect in which partitioning of both solutes increased. During co-solubilization in P20 micelles, many FRMs competed for solubilization between the polyoxyethylene chains in the outer layer of the micelle, thereby resulting in an inhibitory effect for both solutes. Co-solubilization of FRM binary mixtures in SDS micelles often resulted in a synergistic increase in micellar solubility, possibly due to micellar swelling, thereby facilitating partitioning of additional solutes into the micelle. An inverse effect in which the micellar solubility of one solute increased, while the other decreased was observed in both surfactant systems with varying degrees of partitioning depending on the composition of the FRM mixture. The results of this study provide valuable insights into the impact of FRM composition on multi-solute partitioning behaviour and the impact of surfactant type on co-solubilization in micellar solutions.

Liquid crystal and emulsifying properties of carboxymethyl glucoside as water-soluble surfactant

ABSTRACT Three derivatives of glucosides derived from n-dodecyl alcohol in a highly pure β-anomer were synthesised with the aim to yield the liquid crystalline phase at ambient temperature with improved water solubility. Effect of variation in headgroup polarity on thermal properties, liquid crystalline phases, and structures of these derivatives of n-dodecyl β-D-glucoside (β-GlcC12) has been examined through differential scanning calorimetry, optical polarising microscopy, and small- and wide-angle X-ray scattering, respectively. Derivative bearing two carboxymethyl and two hydroxyl groups at the sugar ring i.e. n-dodecyl 2,3-bis-O-[carboxymethyl]-β-D-glucopyranoside (2,3-diCOOH-β-GlcC12) exhibited lamellar phase at the room temperature in anhydrous condition by significantly reduced the melting and clearing temperatures compared to parent compound β-GlcC12. Under excess water condition, 2,3-diCOOH-β-GlcC12 was completely soluble to form a normal micellar solution. We further investigated its foaming performance and emulsifying ability in n-octane, n-dodecane, and n-hexadecane as the oil phase. Both aqueous solution of 2,3-diCOOH-β-GlcC12 emulsified with n-dodecane and n-hexadecane formed oil-in-water emulsion layer of more than 95% of the total system volume with n-dodecane/water system consistently maintains smaller particle sizes and a narrower polydispersity index. This supports the stronger emulsifying ability and better colloidal stability of the 2,3-diCOOH-β-GlcC12 in the n-dodecane/water system than in the n-hexadecane/water system.

Solubilization of n-hexadecane by micellar solutions of trehalolipid - surfactants of biological origin

Objectives. To isolate biosurfactants of glycolipid nature produced by oil hydrocarbon degrading bacteria and to establish their ability to solubilize hydrophobic compounds in the case of n-hexadecane.Methods. Trehalolipids were isolated from bacteria Rhodococcus erythropolis X5 (VKM Ac-2532 D) and Rhodococcus erythropolis S67 (VKM Ac-2533 D) included in the MikroBak biopreparation for the bioremediation of oil-contaminated territories. The genome of R. erythropolis X5 is deposited in the National Center for Biotechnology Information database under GenBank accession numbers CP044283 and CP044284, BioSample – SAMN12818508, BioProject – PRJNA573614, and SRA – PRJNA573614. The content of trehalolipid biosurfactants was estimated by the amount of trehalose in aqueous solutions of biosurfactants using the phenolsulfur method. The surface tension of the obtained aqueous solutions of biosurfactants was determined by the du Noüy ring method using a Kruss K6 tensiometer (Kruss, Germany). The critical concentration of micelle formation was determined by the inflection point on the curves of surface tension dependence on the concentration of the biosurfactant solution. In order to establish the solubilizing ability of biosurfactants, the residual concentration of n-hexadecane in an aqueous sample of different concentrations was determined using a gas chromatographic method of analysis.Results. At a constant surface tension of 24.2 mN/m and 25.0 mN/m for R. erythropolis X5 and R. erythropolis S67, respectively, the critical micelle concentration for both strains was 33 mg/L (3.8 ∙ 10−5 mol/L). The solubilizing effect of Rhodococcus trehalolipid micellar solutions against hydrophobic n-hexadecane was demonstrated by gas chromatographic analysis. The solubilization process was characterized using molar solubilization capacity (Sm), molar solubilization ratio (MSR), micelle–water partition coefficient (Km), and solubilization energy 0 (ΔGS ). It was shown that the solubilization process of n-hexadecane proceeds spontaneously 0 (ΔGS = −35.5 kJ/mol) and more efficiently (Sm = 4.3 mol/mol, MSR = 4.7 mol/mol) than in comparison with other biosurfactants of glycolipid nature.Conclusions. Based on the value of the molar solubilization coefficient, it can be concluded that trehalolipids of the R. erythropolis X5 strain solubilize n-hexadecane in aqueous solutions to a greater extent than compared to other biosurfactants of a glycolipid nature, but are inferior to synthetic surfactants.

Simple simultaneous analysis of various cardiovascular drug mixtures with vincamine: comparative eco-friendly assessment

The development of two eco-friendly analytical methods for the simultaneous determination of eight cardiovascular drugs; hydrochlorothiazide (HCT), captopril (CPL), lisinopril (LSP), valsartan (VAL), atorvastatin (ATR), bisoprolol (BSL), amlodipine (AML) and carvedilol (CVL); alongside with the nutraceutical vincamine (VIC) is essential for sustainable pharmaceutical analysis. This study explores the application of Micellar Electro Kinetic Chromatography (MEKC) and High-Performance Liquid Chromatography (HPLC) for this purpose. In MEKC method, the separation was done using fused silica capillary (41.5 cm × 50 µm id) and a back ground electrolyte consisting of 50 mM borate buffer (pH 9) containing 50 mM sodium lauryl sulphate (SLS) and 10% organic modifier (Acetonitrile). In HPLC method, separation was performed on a ZORBAX Extend-C18 (4.6 × 250 mm, 5 µm) column, using a gradient mobile phase consisting of 50 mM phosphate buffer pH 3 and methanol. Both methods attained good linearity (r ≥ 0.9996) with low values of LOD and LOQ. Both methods were successfully applied in the determination of co-administered single, binary and ternary dosage form of the studied drugs. Moreover, application of various combinations of co-administered dosage forms was achieved in rat plasma, confirming the applicability of these methods in different matrices. The use of micellar solutions in MEKC enhances separation efficiency while reducing the need for organic solvents, aligning with green chemistry principles. HPLC methods were optimized using environmentally benign solvents, ensuring reduced toxicity and waste production. The methodologies were evaluated through green, white, and blue metrics to ensure comprehensive sustainability, considering ecological impact, safety, and practical efficiency. These methods were not only cost-effective and time-saving but achieved high efficiency, sensitivity, and reproducibility making them ideal for routine use in pharmaceutical analysis.

Two-species model for nonlinear flow of wormlike micelle solutions. Part I: Model

We develop a rheological model to approximate the nonlinear rheology of wormlike micelles using two constitutive models to represent a structural transition at high shear rates. The model is intended to describe the behavior of semidilute wormlike micellar solutions over a wide range of shear rates whose parameters can be determined mainly from small-amplitude equilibrium measurements. Length evolution equations are incorporated into reactive Rolie-Poly entangled-polymer rheology and dilute reactive-rod rheology, with a kinetic exchange between the two models. Although the micelle length is remarkably reduced during flow, surprisingly, we propose that they are not shortened by stress-enhanced breakage, which remains thermally driven. Instead, we hypothesize that stretching energy introduces a linear potential that decreases the rate of recombination and reduces the mean micelle length. This stress-hindered recombination approach accurately describes transient stress-growth upon start-up shear flow, and it predicts a transition of shear viscosity and alignment response observed at high shear rates. The proposed mechanism applies only when self-recombination occurs frequently. The effect of varying the relative rate of self-recombination on the rheology of wormlike micelles at high shear rates is yet to be explored.

Alpha-Bisabolol-Loaded Cosmetic Micellar Solution with Cleansing and Antimicrobial Action for Facial Skin Hygiene

The current research is focused on the discovery and optimization of an effective cosmetic carrier of alpha-bisabolol as a first step in the development of a cosmetic product with cleansing and antimicrobial action for facial skin hygiene. A micellar solution of Poloxamer 407 was selected as a cosmetic base because of the good washing ability, easy application, and high tolerability of this polymeric surfactant. The solubilization capacity of a 5% micellar solution with respect to α-bisabolol was investigated by applying varying solubilization techniques and increasing concentrations of the oily active substance. The test samples were subjected to an accelerated physical stability test, viscosimetry, dynamic light scattering (DLS), electrophoretic light scattering (ELS), foamability test, and antimicrobial screening. Over the course of this research, the advantage of the film-hydration method over direct solubilization was demonstrated by the narrower size distribution and smaller hydrodynamic size of the micellar nano-carriers (ranging from 29.02 to 116.5 nm) and the respective higher physical stability of the dispersions. The optimized composition was found to be suitable for application on large skin areas in terms of viscosity in the temperature range from 20 °C to 40 °C (3.4–2.3 mPa.s). Preservation of the washing capacity of the micellar solution in the presence of solubilized α-bisabolol was established. The active composition demonstrated inhibitory activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Candida albicans. This study concludes that the optimal concentration of α-bisabolol to be solubilized in a 5% Poloxamer 407 micellar solution by the film-hydration technique is 1%, considering the desirable physical endurance and antimicrobial activity.

The Interaction Of Homodimer Styrylcyanine Dyes With Sodium Dodecyl Sulfate And Triton X-100.

Solubilization of the styrylcyanine dye Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide) and its homodimers Dbt-5 and Dbt-10 in aqueous solution of sodium dodecyl sulfate and Triton X-100 has been studied by steady state and picosecond time-resolved fluorescence spectroscopy. At low concentration of sodium dodecyl sulfate in solution, between Sbt, Dbt-5 dyes molecules and surfactant ion pairs are formed followed by the formation non-luminescent H-aggregates. The nature of the interaction between molecules of dyes and surfactants has been revealed. The binding constants Ks of the dyes to the surfactants, free energy changes (ΔG0), the number of dye molecules (n) included in a single micelle and photophysical parameters have been determined. The degree of solubilization of dyes in micellar solution of Triton X-100 is higher as compared to sodium dodecyl sulfate and depends on the molecular weight and size of both dye molecules and micelles.

Choline Oxidase and Choline Ionic Liquids in Biocatalytic Heme Peroxidase Cascades

Choline oxidase from Alcaligenes sp. (ChOx) is used to generate hydrogen peroxide in situ from choline‐based ionic liquids (ILs) to fuel peroxidase‐mediated biocatalysis, while mitigating oxidative degradation of the heme‐dependent enzymes. Horseradish peroxidase (HRP) and chloroperoxidase from Caldariomyces fumago (CPO), in combination with the ChOx, are evaluated in enzymatic cascades for the ability of the biocatalytic systems to withstand elevated concentrations of different choline additives in oxidative and halogenative enzymatic assays. The findings are applied in various synthetic scenarios to produce important oxygen‐ and nitrogen‐containing heterocycles, using choline ILs in a dual‐purpose fashion, as a substrate‐solubilizing component in the reaction medium as well as the source for hydrogen peroxide. The ChOx/HRP couple is used to induce intramolecular cyclizations of hydroxamic acids and hydroxycarbamates in a nitroso‐ene‐type pathway with choline dihydrogen phosphate as IL additive. The ChOx/CPO cascade successfully mediates brominative cyclizations of α‐allenic alcohols, while amphiphilic surfactants are employed to turn the aqueous choline propionate IL media into a colloidal suspension. ChOx/CPO partnering is also evaluated in an oxygenative rearrangement of 1‐furylethanol with choline acetate IL. The results show the wide potential of choline oxidase for hydrogen peroxide‐driven biocatalysis with both aqueous and micellar choline ionic liquid solutions.

Micellar mediated preparation of cadmium sulfide (CdS) nanoparticles: Influence of cleavable spacer based cationic gemini surfactant

Cleavable spacer (s = diamido) based cationic gemini surfactant (with different alkyl tail lengths (m) abbreviated as g1; m = 12, g2; m = 14 or g3; m = 16), in aqueous micellar solution, was used to control the size and morphology of cadmium sulfide (CdS) nanoparticles (NPs), via modified chemical precipitation technique. The purity and stability of all CdS NPs were characterized by EDAX, FT-IR, TGA and zeta potential (ζ). By varying the geminis, significant size reduction (2–6 nm), enhanced capping capacity, and higher energy band gap (∼4.1 eV) have been found in CdS-g1 compared to other NPs, by using Dynamic Light Scattering (DLS), TEM, XRD and UV–visible spectroscopy. Photoluminescence (PL) spectra revealed an emission at 525 and 630 nm, showing the effect of geminis m concerning surface states of NP. Additionally, antioxidant and antimicrobial (on Gram-negative (E. coli and P. aeruginosa) and Gram-positive (S. aureus and B. subtilis) strains) activities of CdS NPs were examined by DPPH radical scavenging and agar plating-spot disc inoculation method, respectively. The results recommended a significant antioxidant activity in CdS-g1 with 45.6 %, while, selective antimicrobial activity was obtained on E. coli and S. aureus in all NP systems.

Wormlike Micellar Glycerol Solutions Formed from a Double-Tailed Surfactant with Two Quaternary Ammonium Head Groups.

Herein, a quaternary ammonium surfactant with dual heads and tails, N1,N1,N1,N3,N3-pentamethyl-N3-(3-(2-tetradecylhexadecanamido)propyl)propane-1,3-diaminium dibromide, abbreviated as Di-C14-N2, was synthesized. For the first time, clear observation of aggregate structures formed by surfactants in pure glycerol systems was achieved using cryogenic transmission electron microscopy (cryo-TEM). The system's rheological properties were analyzed using both steady-state shear and oscillatory rheological measurements. The lubricating efficiency of the Di-C14-N2 glycerol solution was assessed for its tribological properties using a tribological wear tester, white light interferometer, and scanning electron microscope. In glycerol, Di-C14-N2 formed long wormlike micelles, which resulted in a glycerol solution with the zero-shear viscosity of 1013 Pa·s at 90 mM, which is the most viscous glycerol system up to now. The system displayed distinct rheological properties from the aqueous system, as evidenced by two intersections in the loss and storage moduli. The formed wormlike micelles in glycerol lead to a significant alteration in the viscoelasticity of the system, thus endowing the Di-C14-N2 glycerol solution with potential as an eco-friendly lubricant. The friction coefficient of the system was found to be 23% lower and the wear rate was 83% lower than that of pure glycerol after the addition of Di-C14-N2. This demonstrates that the addition of Di-C14-N2 greatly improves the frictional properties of pure glycerol. This study offers the possibility of directly observing the aggregate structures formed by surfactants in pure glycerol systems. It contributes to the exploration of the self-assembly behavior of surfactants in nonaqueous polar media, thereby aiding in a deeper understanding of the correlation between molecular structure, mesoscale structure, and macroscopic properties.

Mucosal Penetrative Polymeric Micelle Formulations for Insulin Delivery to the Respiratory Tract.

Effective mucosal delivery of drugs continues to pose a significant challenge owing to the formidable barrier presented by the respiratory tract mucus, which efficiently traps and clears foreign particulates. The surface characteristics of micelles dictate their ability to penetrate the respiratory tract mucus. In this study, polymeric micelles loaded with insulin (INS) were modified using mucus-penetrative polymers. We prepared and compared polyethylene glycol (PEG)-coated micelles with micelles where cell-penetrating peptide (CPP) is conjugated to PEG. Systematic investigations of the physicochemical and aerosolization properties, performance, in vitro release, mucus and cell penetration, lung function, and pharmacokinetics/pharmacodynamics (PK/PD) of polymeric micelles were performed to evaluate their interaction with the respiratory tract. The nano-micelles, with a particle size of <100 nm, exhibited a sustained-release profile. Interestingly, PEG-coated micelles exhibited higher diffusion and deeper penetration across the mucus layer. In addition, CPP-modified micelles showed enhanced in vitro cell penetration. Finally, in the PK/PD studies, the micellar solution demonstrated higher maximum concentration (Cmax) and AUC0-8h values than subcutaneously administered INS solution, along with a sustained blood glucose-lowering effect that lasted for more than 8 h. This study proposes the use of mucus-penetrating micelle formulations as prospective inhalation nano-carriers capable of efficiently transporting peptides to the respiratory tract.

Molecular simulation on solubilization of fullerene C60 by C12E6 nonionic surfactants

ABSTRACT Coarse grained simulations were adopted to describe the encapsulation and dispersion of fullerene C 60 by hexaoxyethylene dodecyl ether (C 12 E 6 ) surfactants. The self-organised structures of C 12 E 6 molecules in water were captured and the characteristics of micelles composed of different number of C 12 E 6 molecules were analysed. We found that C 60 molecules alone or in clusters can spontaneously translate into the hydrophobic core of micelles. One monomeric C 60 can explore the hydrocarbon-chain region of the micelles with different sizes, and two different preferential locations of C 60 are observed. The small C 60 clusters can disaggregate after entering the micelle. Larger C 60 clusters can penetrate into the micelle as solid-like nanoparticles, although they are partially disaggregated. When investigating the self-assembly of C 12 E 6 surfactants and C 60 molecules, we found that it is very difficult to disperse C 60 in the micelle monomolecularly. At high molar ratio of C 12 E 6 /C 60 , colloidal nanoC 60 aggregates form with C 12 E 6 surfactants adsorbed on the surface. Our simulations provide an explanation for the different observations in fullerene solubilization in micellar solutions and give a guideline for further solubilization of pristine fullerene or small hydrophobic molecules with surfacant micelles, which is helpful for the design of new micelle-based delivery vehicles.

Primary alcohol-induced coacervation in alkyl polyglucoside micellar solution for supramolecular solvent-based microextraction and chromatographic determination of phthalates in baby food

This study reports for the first time the phenomenon of supramolecular solvent formation based on alkyl polyglucoside as an amphiphile and primary alcohol as a coacervation agent. The physical properties (density, kinematic viscosity, phase diagram for ternary system) of the supramolecular solvent were investigated, and a mechanism for its formation was proposed. A green and simple microextraction procedure for preconcentration and determination of phthalates in baby foods packaged in plastic packaging was developed as proof-of-concept example. The microextraction procedure assumed separation of analytes from solid phase sample in micellar solution of decyl glucoside and in situ formation of supramolecular solvent for analytes preconcentration after addition of n-heptanol. The determination of phthalates in obtained extracts was implemented by high-performance liquid chromatography with UV–Vis detection. The limits of detection, calculated from a blank test based on 3σ, were determined to be 10 μg kg−1 for dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, and di-n-octyl phthalate. The developed procedure did not require filtration of sample suspension, and assumed the use of green and biodegradable substances for the supramolecular solvent formation across a wide pH range.

Ex-vivo skin retention of crisaborole from microemulsion and micellar formulations

The aim of the present work was to optimize the delivery of crisaborole to the skin, incorporating the drug in topical formulations with a texture suitable also for application to the hairy skin. In particular we focused on microemulsions and micelles. As reference, the concentration of crisaborole in skin layers obtained with the commercial ointment Eucrisa®, was considered. Two microemulsions, one w/o and one o/w, were tested ex-vivo and both produced drug deposition into the skin comparable to the commercial formulation, but with higher delivery efficiency and with a non measurable permeation across the skin. Solutol®, TPGS and Soluplus® at different concentration were used for the preparation of crisaborole micellar solutions. Compared to the commercial formulation, all the micellar systems produced lower drug concentration in the skin layers, with the only exception of Soluplus® 6 %. However, due to differences in drug loading and thus in the applied dose, the delivery efficiency of all the formulation tested was higher compared to the commercial ointment. Moreover with Soluplus® 6 % formulation, a 5-fold increase in the retained/permeated ratio compared to the ointment was obtained. Two-photon microscopy studies showed that Soluplus® 6 % micelles do not permeate intact across the skin but disassemble in correspondence of the tissue surface.

Solvent and media effects on the photophysics of cranad-2 and cranad-58

Alzheimer’s disease (AD) represents the most widespread form of age-related cognitive degeneration, characterized by long-term degenerative damage, cognitive dysfunction, and profound deficits in logical thinking, knowledge acquisition, and interpersonal communication. A principal biomarker of AD involves the emergence and aggregation of β-amyloid (Aβ). Cranad derivatives are fluorescent probes capable of detecting, quantifying, and imaging Aβ aggregates. In this work, the effect of solvent and microheterogeneous environments on the photophysical behavior of CRANAD-2 and CRANAD-58 was investigated employing a large solvent set and several microorganized systems. Both the absorption and fluorescence spectra exhibit a substantial solvatochromic effect, resulting in significant Stokes shifts. Application of linear solvation energy relationships to correlate the fluorescence spectra maxima and the Stokes shift with microscopic solvent parameters suggests significant intramolecular charge transfer during the excitation, as corroborated by the increased dipole moment in the excited state. Generally, fluorescence quantum yields determined for CRANAD-2 exceed those of CRANAD-58 in most solvents, with low values in polar solvents and bigger values in non-polar solvents. Introduction of CRANAD-2 and CRANAD-58 into micellar and vesicular solutions notably augments the fluorescence emission intensity, accompanied by a blue shift in the fluorescence maxima. The fluorescence maxima values observed within microheterogeneous systems closely parallel those reported for interactions between CRANAD derivatives and soluble or aggregated Aβ amyloids which potentially constrains the efficacy of “in vivo” Aβ detection trials, because localization of CRANAD derivatives in non-polar microenvironments present in biological media could interfere with the detection of amyloid fibers.

Coomassie Brilliant Blue G for Smart Colorimetric Determination of the Ionic Surfactants in Triton X-100 Solutions.

The conditions for the smart colorimetric determination of cetylpyridinium chloride and sodium dodecyl sulfate by reaction with Coomassie brilliant blue G (CBBG) have been proposed. The nature of the absorption and fluorescence spectra of aqueous solutions of CBBG as a function of acidity has been investigated. A variety of reagent forms and associations with ionic surfactants have been demonstrated. The composition of the associates formed in the CBBG-cationic surfactant system has been established. The increase in the analytical signal of the cationic surfactant and the stabilization of the colloid-chemical state of the system during reactions in the organized medium of the nonionic surfactant Triton X-100 has been demonstrated. These effects are realized through association in premicellar solutions and as a result of the solubilization of components in Triton X-100 micellar solutions. The addition of long-chain cationic surfactants to the reagent occurs with the replacement of the heteroatom proton. The absorption of CBBG-cationic surfactant associates solutions increases with the length of the cationic surfactant hydrocarbon chain. Ethanol additives decrease the aggregation of CBBG. The technique of cationic surfactant determination has been tested in the analysis of the pharmaceutical. The results show that the simplicity of analytical signal registration with satisfactory correctness and acceptably high sensitivity of determination is an advantage of the developed technique.

Rheo-optics of giant micelles: SALS patterns of cetyltrimethylammonium tosylate solutions in presence of sodium bromide

In this work, we present a systematic study based on Small-Angle Light Scattering (SALS) patterns of the simple shear flow response of semi-diluted solutions of cetyltrimethylammonium tosylate (CTAT; 5.5 wt.% - 0.12 M) in the presence of sodium bromide (NaBr) at different [NaBr]={0,0.12,0.19,0.25,0.3} M concentrations. We evidence a relationship between rheological and light scattering data that reveals a transition into a fast-breaking regime in the dynamics of wormlike micelles formed by the CTAT/NaBr system (Macías et al., 2011; Fierro et al., 2021). This transition into a micellar fast-breaking regime with salt addition ([NaBr]≥0) appears marked by the following features: (i) a decrease in the relaxation time of the material λ0, accompanied by (ii) a decrease of the viscosity level at low shear rates η0 (Macías et al., 2011; Fierro et al., 2021; Schubert et al., 2003; Alkschbirs et al., 2015; Bandyopadhyay et al., 2003). With these, (iii) the formation of butterfly-like patterns is recorded originating from concentration fluctuations, evolution that is accompanied by: (iv) shear banding in the form of non-monotonic flow curves and (v) slow oscillatory transient responses in start-up flow tests captured theoretically with the Bautista–Manero–Puig (BMP) model. In addition, the Cox–Merz rule is fulfilled at molar salt-to-surfactant ratios of R≥1.5. This results in shorter structure-recovery time-scales than the characteristic-time of the flow (Macías et al., 2011; Fierro et al., 2021; Manero et al., 2002). In the case of the elastic modulus G0, the variation was small, which suggests a transition from an entangled to a multiconnected network, as suggested by Kadoma & van Egmond (1997), Kadoma et al. (1997) and Fierro et al. (2021). From a theoretical perspective, we provide predictions for the shear–stress and the first normal-stress growth coefficients in transient start-up simple shear flow using the BMP model. Here, banding R=1.5 solutions display overshot responses at relatively high shear rates (γ̇=10−30s−1), in-line with experimental findings on the start-up flow of wormlike micellar solutions (Soltero et al., 1999; Lerouge et al., 2004; Hu & Lips 2005; Pipe et al., 2010; Mohammadigoushki et al., 2019). Our results are consistent with those reported in other investigations (Macías et al., 2011; Fierro et al., 2021; Schubert et al., 2003; Alkschbirs et al., 2015; Bandyopadhyay et al., 2003; Kadoma et al., 1997; Soltero et al., 1999; Lerouge et al., 2004; Hu & Lips 2005; López-Barrón et al., 2014) and reveal the influence of the Br−-ion used on the mechanical and optical response of the CTAT-NaBr system.

Formation and survival of clay-mediated protocell membranes composed of single-chain amphiphiles in aqueous solutions

Protocell compartments composed of simple amphiphilic molecules could have survived on the clay mineral surfaces which can serve well as plausible sites for prebiotic chemistry on the early Earth. Herein we chose four common single-chain amphiphiles (SCAs), including the anionic surfactant sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS), the cationic surfactant dodecyltrimethylammonium bromide (DTAB) and the zwitterionic lauryl sulfobetaine (LSB)), as model constituents of early membranes to establish a tentative model for protocell compartment. Positively charged Mg2Al-/Mg2Fe-layered double hydroxides (LDHs) and FeS2 are viewed as models of clay minerals. We demonstrate by comprehensively experimental study that unconventional vesicles can be easily promoted in a SCA aqueous micellar solution in the presence of model particles. Morphology evolutions are traced by collecting samples from mixtures of LDHs and SCA aqueous solutions and then recording at different incubation times via negative-staining or cryo-transmission electron microscopy (NS-TEM or cryo-TEM) and dynamic light scattering (DLS). Additionally, the stability of SCA bilayer membranes under possible prebiotic environment are tentatively studied. This work not only offers a robust yet versatile approach for the fabrication of novel vesicles but also provides new insights into the origin of cellular life.

PREPARATION OF LIPID-BASED FORMULATIONS USING LOCAL BEESWAX SOURCED FROM HONEYCOMBS

Solid lipids used in formulation of novel drug delivery systems in most developing countries are sourced from abroad and are quite expensive. Wax from honeycombs is readily available, and is even disposed as waste, but can be utilized as a solid lipid for the formulation of different lipid-based drug delivery systems. This study aims to formulate and compare the features of the solid lipid nanoparticle (SLNs) and nanostructured lipid carrier (NLCs) delivery systems of quinine hydrochloride made with local beeswax (that is beeswax from locally sources honeycomb waste) and other solid lipids sourced from abroad. Local beeswax was first purified by hot bath method. Solidified reverse micellar solutions (SRMS) were prepared by fusion method using Phospholipon®90H and either local beeswax, Softisan®154, foreign beeswax, or stearic acid, separately. SLNs and NLCs of quinine made with SRMS of each of these solid lipids were formulated using hot homogenization method. These SLNs and NLCs were characterized. The average particle size of SLNs and NLCs made with local beeswax was 93.60 ± 4.44 nm and 112.80 ± 3.89 nm, respectively, and was not significantly (p &gt; 0.05) different from the sizes of formulations made from other solid lipids (SLNs: 96.64 to 118.9 ± 4.13 nm and NLCs: 99.68 ± 6.75 to 117.30 ± 4.60 nm). The particles were monodispersed having PDI ranging from 0.281±0.054 to 0.308±0.055. Encapsulation efficiency and loading capacity were generally poor, especially among the SLN formulations. However, SLNs made with local beeswax and stearic acid were able to encapsulate quinine, whereas foreign beeswax and Softisan®154 had zero encapsulation. This study reveals that the features of the SLNs and NLCs made with local beeswax where highly comparable with those formulated with the imported solid lipids. Therefore, local beeswax can serve as a suitable affordable and available alternative to other imported solid lipids for formulating different lipid drug delivery systems.

Micelle-modulated ribonuclease-like activities of oxo-bridged binuclear copper(ii) complexes with novel imidazole derivatives

Three bis-tridentate imidazole derivatives as ligands and their alkoxo-bridged binuclear copper(II) complexes (1, 2 and 3) were synthesized and characterized. Single crystals show that furan or thiophene moiety of 2 or 3 is free without a coordination with the central copper. Five-coordinated structure of 1 is constructed via two Cu-N and three Cu-O coordination bonds involving the participation of phenolic oxygen, alkoxo-bridged oxygen and the one carboxylate oxygen. Furthermore, catalytic reactivity of the as-synthesized binuclear complexes was evaluated for the transesterification of classic RNA model HPNP (2-hydroxypropyl-4-nitrophenyl phosphate). Overall, three complexes displayed the almost similar activity in both non-micellar and micellar solutions. HPNP transesterification achieved more obvious acceleration in micellar solutions of three kinds of cationic surfactants. All of three complexes obtained relatively good reactivity in CTAB micellar solution, respectively achieving approximately 804-fold (for 1), 762-fold (for 2) and 785-fold (for 3) rate enhancement compared to background rate of HPNP spontaneous cleavage. The as-synthesized binuclear complexes displayed approximately two times dominative activity in CTAB micellar solution over that in the non-micellar system. However, to some extent the introduction of amphoteric n-lauroylsarcosine sodium (LSS) and non-ionic polyoxyethylene lauryl ether (Brij35) inhibited the catalytic transesterification of HPNP. This study is beneficial to the design and application of novel mimic esterolases.